Vibrating screens are commonly used to separate excess water from particulate materials, for example in sand quarrying to remove excess water from sand following grading and/or washing processes, and are used to sort, grade or classify particulate material, such as sand.
A typical vibrating screen comprises a frame, defined by a pair of substantially parallel side walls interconnected by transversely extending bridging members, upon which is mounted a substantially horizontal polyurethane deck having small openings or slots for water and/undersize particles to pass through.
The frame is mounted on a base via resilient linkages, such as springs, and the frame, and thus the deck, is typically vibrated by means of a pair of counter rotating rotors defining eccentric masses, driven by one or more drive motors, to impart circular or reciprocating vibratory motion to the deck.
Dewatering screens are used to separate excess water from particulate materials and are used in sand quarrying to remove excess water from sand following grading and/or washing processes.
A typical dewatering screen comprises a frame upon which is mounted a substantially horizontal polyurethane deck having small openings (approximately 0.25 mm diameter) for water to pass through. The deck is vibrated at high frequency to shake out excess water through the openings and to convey the material across the deck to one end of the screen whereby the dry material is discharged over the top of a weir onto a conveyor or into a collection hopper.
Screens are also used to grade particulate material, in particular sand, by particle size. In a grading screen the deck is arranged at a predetermined slope and material to be graded is delivered onto an upper end of the deck, typically entrained in a flow of water. The deck is vibrated at high frequency to convey the material over the deck and to cause undersize material (and water) to pass through the openings, oversize material being discharged from a lower end of the deck onto a conveyor or into a collection bay or hopper for subsequent dewatering. It is known to provide grading screens wherein the angle of declination of the screen deck varies along its length in order to control the speed of movement of material over the screen deck, for example to slow the material to allow it to be graded more effectively adjacent a lower end of the deck (such as that shown in CN201441973). Such screens are typically referred to as “banana screens” due to their arcuate profile.
However, no prior art screens have been provided that can be effectively grade and also dewater a particulate material on a single deck.